<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    *{
      margin: 0;
      padding: 0;
    }
    .container{
      background-color: red;
      width: 400px;
      height: 400px;
      position: relative;
      margin-left: 200px; ;
    }
    .son1{
      background-color: green;
      width: 100px;
      height: 100px;
      position: absolute;
      margin-left: 100px; 
      margin-top :20px;;
    }
   .son2{
      background-color: blue;
      width: 100px;
      height: 100px;
      position: absolute;
    }
  </style>
</head>
<body>
  <div class="container">
    <div class="son1"></div>
    <div class="son2"></div>
  </div>
</body>
</html>